feat: replace email flows with in-app notifications

Add recipient notification detail and filtering, a queued admin composer, and contextual automatic titles. Retire email delivery, obsolete auth routes, newsletter data, and related templates and settings.

apps/notifications/api/schemas.py

@@ -9,10 +9,10 @@ class NotificationSchema(Schema):
     type: str
     title: str
     message: str
+    has_body: bool = False
     level: str
     created_at: datetime | str
     is_seen: bool
-    delete_on_seen: bool
     action_url: str | None = None
     entity_type: str | None = None
     entity_id: int | str | None = None
@@ -25,6 +25,10 @@ class NotificationListSchema(Schema):
     notifications: list[NotificationSchema]
 
 
+class NotificationDetailSchema(NotificationSchema):
+    body_markdown: str | None = None
+
+
 class NotificationSeenIn(Schema):
     id: str